The mammalian gastrointestinal tract comprises the esophagus, stomach, small intestine, and colon. Physicians image the interior of the gastrointestinal tract to aid in the diagnosis and treatment of many illnesses such as ulcers, growths, cancers and bleeding spots. More specifically, these conditions include colorectal cancer, colonic polyposis, inflammatory bowel disease, irritable bowel syndrome, Barrett's esophagus, peptic ulcer disease and dyspepsia.
Colorectal cancer, for example, is the second leading cause of cancer death in the United States, with 133,500 new cases detected in 1996, 54,900 (41%) of which resulted in death. (Agency for Health Care Policy & Research (AHCPR) Research Activities 200:15-16, 1997.) Survival rates improve and treatment costs decline with early detection of the process. (Brown, M. L. and Fintov, L. The economic burden of cancer. In Greenwald, P. Kramer, B. S., and Weed, D. L., eds Cancer Prevention and Control. New York, Marcel Decker, pp. 69-81, 1995. Healthy People 2000: Nutritional Health Promotion and Disease Prevention Objectives. U.S. Department of Health and Human Services, Public Health Service, DHHS Publication No. (PHS) 91-50212, p. 423, 1991.) However, regular screening for colorectal cancer is not performed for the vast majority of the populace due to the high cost of such programs and, more importantly, the reluctance of a healthy population at risk to undergo an invasive procedure again and again for surveillance against cancer. As a result, over two-thirds of patients are diagnosed with advanced disease. (Eddy, D. M. Screening of colorectal cancer Ann. Int. Med. 113:373, 1990).
The only low-cost noninvasive screening tests for colorectal cancer are fecal occult blood tests, which look for the presence of fecal occult blood in stool specimens. These tests exhibit poor sensitivity due to the fact that malignant growths of the colon have to be fairly large before they start to bleed. Furthermore, there are many other reasons for bleeding into the gastrointestinal tract (e.g., ulcers) which lead to low specificity of the test and a high probability of false positives. (Eisner, M. S., and Lewis, J. A. Diagnostic yield of positive FOBT found on digital rectal examination. Arch. Int. Med. 151:3180, 1991. Rockey, D. C., Koch, J., Cello, J. P., Sanders, L. L., McQuaid, K. Relative Frequency of Upper Gastrointestinal and Colonic Lesions in Patients with Positive Fecal Occult-Blood Tests.) Even with the poor characteristics of fecal occult blood tests, the American Cancer Society estimated that the regular use of the test in men over age 50 could produce a 15% reduction in mortality. (Agency for Health Care Policy & Research (AHCPR) Research Activities 200:15-16, 1997.)
The most common diagnostic procedure for colonic examination is colonoscopy. This procedure involves the optical examination of the entire colon using a device known as a colonoscope. A colonoscope comprises a flexible tube containing a fiber optic imaging and illuminating device and a device to resect portions of the surface of the intestinal tract. The colonoscope is inserted into the rectum and can be maneuvered to the ileo-cecal junction (the start of the colon). The operator views the image on a video display. The medical team performing this procedure usually comprises a gastroenterologist, specially trained nurses and at times an anesthesiologist. Polyps (tumors) are identified visually and biopsied. If examination of the specimen reveals malignancy, a surgical team resects the regions containing the tumors. Usually, this is followed by a period of chemotherapy, administered to fight unobserved or secondary tumors; annual colonoscopies may be prescribed. Considering the cost of the colonoscopy alone, a yearly colonoscopy for all patients over age 48 for instance, would be prohibitively expensive. Colonoscopy for asymptomatic patients is seldom prescribed.
The sigmoidoscope is similar to a colonoscope, but can only be used to image the lower ⅔ of the colon. Although simpler than a colonoscope, its operation still requires the presence of a highly trained physician and often requires sedation.
The esophagogastroduodenoscope is used to image the upper gastrointestinal tract, namely, the esophagus, the stomach and the duodenum. It is inserted through the mouth. Again, its operation requires the presence of a highly trained physician and often requires sedation.
The esophagogastroduodenoscope is used to identify ulcers, gastritis, AVMs, esophagitis, varices, duodenitis, Barrett's esophagus, hiatal hernias and tumors. The esophagogastroduodenoscope procedure is performed on patients with a variety of symptoms that include nausea, vomiting, abdominal bloating, abdominal pain, heartburn, reflux, family history of cancer, jaundice, weight loss, anemia, and gastrointestinal bleeding. A majority of those procedures are diagnostic. Considering the cost of endoscopy and the sedation requirement, it would be prohibitively expensive to perform esophagogastroduodenoscopy on all patients with symptoms.
The push enteroscope is used to image the third and fourth portions of the duodenum and the proximal jejunum. It is inserted through the mouth. Its operation requires the presence of a highly trained physician and requires sedation. The push enteroscope may be used to detect arteriovenous malformations and small intestinal tumors.
The endoscopic retrograde cholangiopancreatograph procedure is done to visualize, to treat, and to diagnose pancreatic and biliary diseases. The endoscopic ultrasound and transesophageal ultrasound are used to image the esophagus, adjacent mediastinal structures, lungs, pancreas, aorta and other vessels, colon and heart. These techniques allow for tissue aspiration through a fine needle. Each of these procedures involve the passage of and endoscope through the mouth. Their operation requires the presence of a highly trained physician and a lot of sedation.
The present invention is a type of non-tethered device that is ingested by the patient, thereby passing through the entire gastrointestinal tract, sending images and data through a telemetry means. There are several prior systems that use an ingestible device to provide data on the internal state of a patient. The Heidelberg capsule relays pH information through a radio frequency (RF) link, and can release medicament on a signal from an external transmitter. The Konigsberg capsule monitors temperature and uses a RF link. The Cortemp pill, which is commercially available at this time, also monitors the body temperature, but uses a near-field magnetic link.
More sophisticated approaches such as colonoscopy and related gastrointestinal imaging methods, namely, sigmoidoscopy and esophagogastroduodenoscopy, are more effective because they can identify abnormalities before the occurrence of late-stage symptoms (e.g., blood in the stools for colonic tumors or tarry stools for peptic ulcers) However, these methods see limited use for several reasons. One, they are invasive and uncomfortable to the patient, requiring sedation so that a flexible fiberoptic tube can be inserted into the tract. This is a major limitation of these tests in their application to healthy asymptomatic individuals for repeated examinations (every 1-3 years).
Secondly, these tests are expensive, requiring the presence of a physician and other personnel. Third, they are inconvenient, requiring the patient to take a purgative, fast overnight, and remain incapacitated during the procedure.
Thus, there is a medical and economic benefit for an inexpensive, noninvasive, miniature, ingestible imaging or diagnostic device that allows the patient to use the device while still performing the normal activities of daily living. Furthermore, it would eliminate the need for highly trained personnel for its operation. In light of the high cost of current imaging methods (and their subsequent limited and late-stage application), hospitals, clinical laboratories, and Health Management Organizations (HMOs), will be able to employ these devices as a cost-containment strategy.
Accordingly, it has been considered desirable to develop a new and improved miniature diagnostic and therapy device which would overcome the foregoing difficulties and others and meet the above-stated needs while providing better and more advantageous overall results.